1. Technical Field
The present disclosure relates to a bonding device for bonding electronic components, such as wafers, to each other using a thermal compression bonding technique.
2. Background Art
Some existing chip thermocompression-bonding tools include a metal block mounted on the lower end of a tool body thereof. A ceramic holder is mounted on the lower end of the metal block. The ceramic holder is sintered together with a ceramic heater and a ceramic indenter. The linear expansion coefficient of the ceramic holder is substantially the same as that of the ceramic heater and the ceramic indenter. In addition, the thermal conductivities of the ceramic holder and the ceramic indenter increase from the ceramic heater towards a pressure-applying surface of the ceramic indenter, and decrease towards a mounting surface of the ceramic holder (refer to Patent Document 1 listed below).
In such chip thermocompression-bonding tools, little heat is transferred to a tool body and a mounting portion of the ceramic holder and little space is required for the ceramic holder, the ceramic heater, and the ceramic indenter. Accordingly, extension of the tool body having a parallelization adjustment function due to thermal expansion and deviation of the degree of parallelization (distortion) can be eliminated. In addition, a temperature difference between neighboring layers of the ceramic holder can be reduced (i.e., the amount of heat is not rapidly reduced, but is gradually reduced) by sintering the ceramic holder so that the thermal conductivity is gradually reduced from the ceramic heater to the ceramic holder mounted portion and employing a lamination structure having the same or substantially the same thermal expansion coefficient. Thus, heat deformation of the ceramic indenter, the ceramic heater, and the tool body can be reduced. In this way, this lamination structure allows heat to be easily transferred to the chip pressure side while allowing little heat to be transferred to the side of the tool body having a parallelization adjustment function. In addition, this lamination structure has the same or substantially the same thermal expansion coefficient. Consequently, the problems caused by heat can be solved, and therefore, the chip thermocompression-bonding tool can be assembled with a high degree of accuracy (refer to Patent Document 1 listed below).
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 2000-332061
To achieve such a structure, a sintered body having lamination structure with varying thermal conductivity needs to be manufactured. Accordingly, the manufacturing process is complicated. In addition, when the thermal expansion coefficient is the same, deformation occurs in portions where a temperature gradient is present. Therefore, even if the temperature difference between the neighboring layers can be reduced, a relatively large amount of heat deformation occurs. Consequently, the flatness of an attractive surface of a chip for a small workpiece can be maintained. However, if the above-described existing technology is applied to a wafer having a large area, it is difficult to maintain the flatness of an attractive surface for a wafer. In addition, the ceramic heater is not thermally isolated from the tool body by a space. Accordingly, even when the thermal conductivity of a material is reduced, and heat transfer to the tool body is reduced, the effect is limited. As a result, the heat capacity of a portion to be heated is unnecessarily increased. Thus, when the existing technology is applied to a wafer having a large area, a time required for heating and cooling is disadvantageously increased.